I was lucky in past and never have problem with my domain names and domain resellers, and didn't know that your domain can be hold or locked with some providers.
I did purchase domain with hosting and after some period had that domains moved to another provider without any problems (just be sure that your domain isn't expired).
Why I did that, because I found out that domain name is expensive with that provider. For 1st year was free after that was $4-7 expensive then other providers.
You can find hosting providers with free domain name for 1st year, lifetime or discount for 1st year. Offers with 1st year discount or free is good for one year but look or ask how much will cost domain after promo period, many provider over sale domains after that period.
For example discount price is $5-$7 after that is $14-17 year.
Free lifetime domain offers with hosting package can help you to save time looking for domain provider and have all in one roof. You know how much you will pay every year. And you can later transfer domain. (I don't know what hosting company keeps domains)
Its all up to you, choose to have or not domain and hosting with same company / provider / reseller .